Brutally low temperatures and frightening wind chills (49 below zero in Chicago! 65 below zero in northern Minnesota!) led the US Postal Service to suspend deliveries Wednesday in parts of 10 states in the Great Plains and Midwest out of concern for workers’ safety.

About 212 million people — or 72% of the continental US population — will see temperatures drop below freezing over the next few days. And more than 83 million Americans — about 25% of the US population — will suffer subzero temperatures at some point between Wednesday and Monday.

While most of the Midwest will see frigid temperatures, Chicago will be “the epicenter of the extreme cold,” CNN meteorologist Dave Hennen said.

Chicago could reach a record low temperature of 27 below zero by Thursday morning. Its daytime high Wednesday is forecast to be 15 below zero.